The present invention relates generally to a hitch for a work machine, and more particularly to an adjustable link assembly for a hitch.
Agricultural work machines, such as tractors, typically include a hitch arrangement for coupling a work implement to the work machine. The hitch arrangement generally includes three link assemblies. One link assembly is interposed the work machine frame and the implement and is adjustable in length to control the angle of the implement with the horizontal in the working position. This link is sometimes referred to as a pitch link. The other two link assemblies are used to connect a pair of draft arms to a pair of rocker arms and are generally called lift links. These link assemblies are also adjustable in length to control the raise and lower positions of the implement.
Heretofore, various designs have been utilized to accomplish the above adjustments. These designs have included devices wherein relative rotation between an internally threaded sleeve and an externally threaded rod provides such adjustment. For example, a wrench can be used to accomplish the rotation. However, utilizing a separate tool such as a wrench is inconvenient for the operator and the tool must constantly be carried in order to make the appropriate adjustments. Additionally, the problem of the length of the link assembly inadvertently changing during operation is not addressed. In particular, vibrations generated during operation are communicated to the internally threaded sleeve and the externally threaded rod and can cause relative rotation there between. As a result, the length of the link assembly inadvertently changes during operation, which can adversely effect the performance of a work function. This requires some type of locking mechanism to hold the internally threaded sleeve and the externally threaded rod from rotating relative to one another.
In an attempt to address the aforementioned problem, some coupling arrangements include a latch for preventing the relative rotation between the internally threaded sleeve and the externally threaded rod. Some of these latches are designed so that when they are unlatched they can function as a handle, which is attached to the internally threaded sleeve or the externally threaded rod. This handle is grasp and rotated by the operator of the work machine so as to cause relative rotation between these elements and thereby change the length of the link assembly. One such link assembly is disclosed in U.S. Pat. No. 4,194,757 issued Mar. 25, 1980 and assigned to the Allis-Chalmers Corporation Milwaukee, Wis. A drawback with this type of latch is that it is permanently attached to the link assembly, which significantly decreases the flexibility with which the latch can be positioned during the time it is used as a handle. As a result, these types of latches are difficult to use and decrease the efficiency with which an operator can adjust the length of the link assembly. A further design that appropriately addresses this problem is U.S. Pat. No. 6,056,069 issued May 2, 2000, assigned to the owner of the present application, however it utilizes a separate pin to hold the handle in the locked position.
The present invention is directed to overcoming one or more of the problems as set forth above
In one aspect of the present invention an adjustable link assembly is provided that includes a body portion that has a polygonal shape in cross-section and an internally threaded bore. A first rod threadably engages the internally threaded bore of the body portion. A second rod engages the internally threaded bore of the body portion. A locking mechanism that includes a lever and an engagement portion, the engagement portion has an internal passage. The internal passage has a polygonal shape larger than and slidably engaging generally the entire length of the polygonal shape of the body portion.